Do octopuses have three hearts?
Yes. An octopus has three hearts: two pump blood through the gills, and one pumps it around the rest of the body. Its blood is blue, too.
Going deeper
The two branchial hearts push blood through the gills to pick up oxygen. The systemic heart then sends it around the body. Oddly, the systemic heart stops beating when an octopus swims, which may be one reason they prefer crawling.
Octopus blood is blue because it carries oxygen using a copper-based molecule called hemocyanin, rather than the iron-based hemoglobin that makes our blood red.